Do not use the flow style in the diff output

[AlekSi]

Description

Closes #4157.

Readiness checklist

• I added/updated unit tests (and they pass).
• I added/updated integration/compatibility tests (and they pass).
• I added/updated comments and checked rendering.
• I made spot refactorings.
• I updated user documentation.
• I ran task all, and it passed.
• I ensured that PR title is good enough for the changelog.
• (for maintainers only) I set Reviewers (@FerretDB/core), Milestone (Next), Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[codecov]

Codecov Report

Attention: Patch coverage is 74.00000% with 13 lines in your changes are missing coverage. Please review.

Project coverage is 74.48%. Comparing base (75f5a74) to head (b840aa8).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4170      +/-   ##
==========================================
- Coverage   74.89%   74.48%   -0.41%     
==========================================
  Files         354      354              
  Lines       23014    23038      +24     
==========================================
- Hits        17236    17160      -76     
- Misses       4465     4556      +91     
- Partials     1313     1322       +9     

Files	Coverage Δ
internal/bson2/document.go	63.88% <100.00%> (+1.03%)	⬆️
internal/bson2/logging.go	90.14% <100.00%> (-0.14%)	⬇️
internal/wire/msg_body.go	50.00% <ø> (ø)
internal/wire/op_msg.go	70.08% <100.00%> (+0.78%)	⬆️
internal/wire/op_query.go	53.40% <100.00%> (+3.40%)	⬆️
internal/wire/op_reply.go	60.86% <100.00%> (+3.72%)	⬆️
internal/bson2/raw_document.go	81.81% <66.66%> (-2.19%)	⬇️
internal/clientconn/conn.go	51.35% <0.00%> (ø)
internal/bson2/array.go	61.01% <0.00%> (-2.15%)	⬇️
internal/bson2/raw_array.go	28.57% <0.00%> (-1.74%)	⬇️

... and 19 files with indirect coverage changes

Flag	Coverage Δ
filter-false	?
filter-true	67.40% <38.00%> (-0.74%)	⬇️
hana-1	13.78% <38.00%> (+<0.01%)	⬆️
integration	67.40% <38.00%> (-0.78%)	⬇️
mongodb-1	4.84% <0.00%> (-0.01%)	⬇️
mysql-1	?
mysql-2	?
mysql-3	?
postgresql-1	46.14% <38.00%> (-0.09%)	⬇️
postgresql-2	48.90% <38.00%> (-0.15%)	⬇️
postgresql-3	48.82% <38.00%> (-0.14%)	⬇️
sqlite-1	45.29% <38.00%> (-0.15%)	⬇️
sqlite-2	48.05% <38.00%> (-12.00%)	⬇️
sqlite-3	48.03% <38.00%> (-0.13%)	⬇️
unit	32.97% <74.00%> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[rumyantseva]

LGTM